GRT EIS Tachometer Readings

[Friesen5]

Good Morning,

I just had my Jab 2200 rebuilt by Arion Aircraft. I flew it for a few short flights yesterday. The tach reading is off, giving me an over rev indication on my EIS. I took some careful measurements incrementally up to 2000 rpm EIS indicated. I compared this to an optical handheld. The difference was a consistent factor of 1.2; the EIS showing 1.2 more RPM over 9 readings. Prior to sending the engine to Arion, the tach was consistent over 17 years of use.

So, what could have changed while my airplane sat 3 months waiting for the engine? Any suggestions on how to bring it back to normal.

I should add that I got a new prop, identical to the Sensenich 54-50 that was on it. That might account for a small difference, but I doubt a 20% difference.

[Skippydiesel]

Unfortunatly I do not have an answer for you but would ask - Has the change resulted in an increase/reduction in performance ?

It seems to me there are a number of factors that may have produced a diffrent RPM read out to that of the past.

The engine is now more efficient.
The Optical tacho is not accurate (I have one like this).
Ambient air temperature can affect the performance of both engine & prop.
After 17 years of potential improvements, the prop may be delivering better performance.